Subsidence and measures in the polders of the Netherlands

Abstract The Netherlands consists for 65% of polders. Impoldering activities started in the beginning of the 11th century with impoldering of coastal lowlands. In the 13th century, a start was made with reclaiming of lands gained on the sea and since early 16th century with draining of lakes. Up to several metres in depth, soils consist primarily of peat and or clay. Underneath is a thick sandy layer, with lenses of clay. Especially in peat polders, subsidence and oxidation have been significant, up to 5 m, and is still going on. In clay polders, most of the subsidence took place in the first decennia after reclamation. Maximum subsidence in these polders has been 1.25 m. Over centuries, various measures have been taken to cope with the subsidence problems. These measures consist first of all in water management measures related to management not only of the subsidence process, but also of special measures with respect to buildings, structures and infrastructure. The paper presents a review of the subsidence process in the different types of polders, as well as of measures that over the centuries have been taken to cope with the developments in the polders and to cope with subsidence problems.